Salt compositions and their preparation



United States PatentOfitice 3,163,604 Patented Dec. 29, 1964 3,163,604 SALT COWDSITIQNS AND IR PREPARATION Alan Sander Dublin, Cincinnati, Ohio, assignor to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed June 29, 1961, Ser. No. 131,039

4 Claims. (Cl. 252--35) This invention relates to a process for preparing salt compositions, to the compositions so prepared, and to their uses. In one particular aspect, this invention rclates to a process for preparing salt compositions from preformed metal acetate salts and free organic acids.

The salt compositions of this invention can be added to lubricating oil to thereby form oil compositions which can then be used as fluid lubricants having high load carrying ability and reduced wear characteristics. They can also be used in oil to make thickened lubricating greases, and as extreme pressure agents, and antiwear additives. Another use of the present salt compositions is in oil to make fracturing fluids.

Lubricants, particularly lubricating greases of the solid and semifluid types, commonly comprise mixtures of metal salts of organic acids having from 1 to 30 carbon atoms. As a matter of convenience and economics, the commercial preparation of these lubricants is usually carried out in situ in the lubricating oil. This means that organic acids of low molecular weight and acids of intermediate or high molecular weight, and a metal base, for instance, lime, are all coneutralized in an oil menstruum or medium. There are several disadvantages inherent in the in situ preparation. These are: Special equipment is needed to assure proper mixing and reaction between the acids and the base; complete neutralization is difficult to obtain because the reaction is often incomplete and this leads to poor quality products. It is now known that the quality of compositions of this type, when used as lubricants, is considerably enhanced by a reduction of particle size of the metal salt of the low molecular weight organic acid, e.g., calcium acetate. There are some recently discovered techniques for achieving a small particle size for the low molecular weight acid salt. These techniques generally comprise mixing oil, preformed metal acetate, and preformed salts of C to C fatty acids in the presence of a small amount of a polar material. The mixture is heated to disaggregate the preformed metal acetate. Alternatively, Where either of the preformed components contain Water of hydration, the Water of hydration can be disassociated from either the calcium acetate or salt to act as the polar material, thus insuring particle size reduction.

While the use of a preformed salt and metal acetate in the manner discussed above presents several important advantages over the conventional in situ preparation, even that process can be further improved. Preformed salts of many common acids are not readily available commercially. The instant invention overcomes this scarcity since it utilizes the free acids, of which many varieties are available commercially and at relatively inexpensive prices. Thus, the decided advantages of using preformed components to obtain high quality lubricants are retained, with the additional advantage of being able to use materials commercially available on a relatively Wide scale.

An additional advantage of this invention is that an approximately neutral product can be obtained. Excess basicity tends to make a lubricant gritty and form a crust on storage. Excess acidity usually has an undesirable eflect on the structural stability of the lubricant and gives it a false hardness.

In brief, the present invention is generally carried out by dispersing a metal acetate salt and a free carboxylic acid in oil and heating the dispersion with agitation to form a homogeneous mass at a temperature of from to 600 F., e.g. 245 to 450 F., and then allowing the mixture to cool where it can be milled if desired. Free acetic acid released from the metal acetate salt will boil oif at temperatures above about 244 F., and the tem-' perature of preparation can be maintained at a sufli ciently high level to insure expulsion from the reaction mass of all such acid when desired. When the acetic acid is boiled off, a substantially neutral product is obtained. For applications not requiring a substantially neutral product, the free acetic acid need not be boiled off. Suitable mills include the Morehouse mill, Charlotte colloid mill, Manton Gaulin hom'ogenizers, and the like.

High and/ or intermediate molecular weight carboxylic acids are useful for the purposes of the invention, particularly those having 7 to 30 carbon atoms and, preferably, those having 7 to 22 carbon atoms per molecule. These acids may be derived. from saturated or unsaturated, natural or synthetic, fatty materials. The fatty acids normally used in the manufacture of conventional greases, particularly the more saturated acids, are preferred. Examples of such acids include stearic, hydroxy stearic, dihydroxy stearic, polyhydroxy stearic, other saturated hydroxy fatty acids, coconut acids, hydrogenated fish oil, and tallow acids, etc. However, unsaturated acids, such as oleic, ricinoleic, and similar acids may also be used. v

The metal acetate salts include those acetate salts prepared from the alkaline earth metals, particularly calcium, barium, and magnesium, as Well as those prepared from the alkali metals and the heavy metals of Groups I, II and IV of the Periodic System, particularly copper, zinc, and lead.

Calcium acetate is the preferred salt and that includes the anhydrous form as well as all the different hydrated forms.

Oil compositions will comprise about 0.001 to 40 wt. percent of the combined amount of metal acetate and fatty acid, said wt. percent being based on the weight of the entire oil composition. When used as a fluid lubricant, this combined amount will be about 0.2 to 20 Wt. percent, and when used as greases, about 10 to 40 wt. percent of the entire oil composition. The above weight percents are based on the weights of the starting materials prior to heating.

The metal acetate and acids will be chosen so that the mole ratios of their acid radicals will be in the range of about 4:1 to 40:1, e.g., 6:1 to 25:1 ofacetic acid to the medium or high molecular Weight acids.

Mineral lubricating oils, as well as synthetic oils of the synthetic hydrocarbon, hydrocarbon polymer, ester, complex ester, formal, mercaptal, polyalkylene oxide, silicon, or similar types may be used including such specific oils as di-2ethyl hexyl sebacate, (ll-Cg-OXO azelate, etc.

Phenyl-alpha-naphthylamine is a desirable ingredient in finished lubricants. It acts as an oxidation inhibitor. Other oxidation inhibitors may be used if desired. Conventional tackiness agents, extreme pressure compounds, viscosity index improvers, corrosion inhibitors, and the like, may also be included.

The salt compositions obtained from the process of this invention may be added to metal working lubricants such as cutting oils, drying compounds, forging compounds, etc. of the mineral oil or emulsion type to improve their extreme pressure characteristics. These lubricants can then be used in the same manner as conventional lubricants would be used. They are particularly useful for those applications requiring good extreme pressure properties.

Oil compositions of this invention can be prepared with, or subsequently diluted with, additional oil so that they contain from about 0.001 to 1.0 wt. percent, preferably about 0.01 to 0.10 wtv percent, of the combined amount of metal acetate and acid when they are to be used as fracturing fluids. These weight percents are based on the weight of the metal acetate and free acid prior to heating.

Fracturing fluids are used in fracturing subsurface formations to increase or initiate the production of oil. Well fracturing is the splitting of rock by pressure. Hydraulic pressure is applied to the rock surrounding the well bore and creates compressive forces on the rock around the hole. When these forces become great enough, they force the rock apart and start the split (i.e., fracture) which is lengthened by a fluid pumped into the hole. A fracturing fluid is such a fluid and it is pumped into the hole by the usual well completion pumps. A fracturing fluid holds a propping material, such as sand, in suspension while being pumped down the well. It deposits the propping material into the cracks of the formation thus preventing closure or clogging of these fissues once the hydraulic pressure is released and the treatment discontinued. Therefore, the fracturing fluid will flow into the cracks of the formation, but desirably should not seep into the surrounding pores. It also should not plug the pores of the formation, or the capacity of the formation to produce oil will be impaired.

This invention is illustrated by reference to the following specific examples which show various embodiments of the invention.

xample l The process of this invention was carried out as follows. 1568 grams of a mineral lubricating oil having a viscosity of 55 SUS at 210 F. and 107 grams of Wecoline AAC fatty acids (a mixture of about 28 Wt. percent caprylic, about 46 wt. percent capric and about 26 wt. percent lauric acids derived from coconut fatty acids) were charged into a Hobart mixer bowl. The mixture was heated to 150 F. with agitation and 386 grams of calcium acetate monohydrate were added. The mixture was then heated to 430 F. to drive off the Water of hydration and the acetic acid that formed. The heat was removed and 20 grams of phenyl-alpha-naphthalamine were added at 300 F, The product was milled on the three-roll mill and remilled on the Morehouse mill. The properties of the resulting lubricants are as follows.

ASTM penetration at 77 F., mm./l:

After 3-roll milling- Grease Neutralization No.: 0.07 wt. percent based on weight of the sample tested, as NaOH.

Example 11 To 150 grams of Weccoline AAC acids in 2271 grams of the mineral oil of Example I at a temperature of 150 F were added 516 grams of calcium acetate half-hydrate. The mixture was heated in the Hobart mixer bowl of Example I to 350 P. where the acetic acid boiled off. It was then allowed to cool to 300 F. and 30 grams of phenyl-a-naphthylamine were added. The mixture was then allowed to cool to ambient temperature and milled through a Morehouse mill. Penetrations and neutralization number were as follows.

ASTM penetrations at 77 F, mun/10:

After Morehouse miliing Worked 60X 330 Worked 10,000 375 Grease Neutralization No; less than 0.01 wt. percent based on the sample tested as NaOH.

The product of Example 11 was also tested in the Timken machine for E? properties. The product carried a 45lb. weight without scoring the test block.

Example III ix hundred and three grams of calcium acetate-half-..

ASTM penetration at 77 F, mm./10:

After Morehouse milling- Worked 60X 260 Worked 10,000X 344 What is claimed is:

1. A process for preparing salt compositions which comprises:

(a) heating a major proportion of oil and from 0.001 to 40 weight percent of a mixture of preformed metal acetate and C to C carboxylic acid to an acetic acid releasing temperature of from to 600 B, said oil being otherwise free of a basically reacting compound,

(b) said metal being selected from the group consisting of alkali metals, alkaline earth metals, and the heavy metals of Groups 1', II and IV of the Periodic System, and

(c) said metal acetate and said carboxylic acid being present in amounts such that the mole ratio of the acetic acid precursor of the metal acetate to the carboxylic acid is from about 4:1 to 40:1.

2. A process as defined in claim 1 wherein said metal is an alkaline earth metal.

3. A process as defined in claim 2 wherein said heating is suflicient to boil off substantially all of the acetic acid formed.

4. A process as defined in claim 1 wherein said metal is calcium and said temperature is from 245 to 450 F.

References Cited in the file of this patent UNITED STATES PATENTS 2,417,428 McLennan Mar. 18, 1947 2,735,815 Morway Feb. 12, 1956 

1. A PROCESS FOR PREPARING SALT COMPOSITIONS WHICH COMPRISES: (A) HEATING A MAJOR PROPORTION OF OIL AND FROM 0.001 TO 40 WEIGHT PERCENT OF AMIXTURE OF PREFORMED METAL ACETATE AND C7 TO C30 CARBOXYLIC ACID TO AN ACETIC ACID RELEASING TEMPERATURE OF FROM 100 TO 600*F., SAID OIL BEING OTHERWISE FREE OF A BASICALLY REACTING COMPOUND, (B) SAID METAL BEING SELECTED FROM THE GROUP CONSISTING OF ALKALI METALS, ALKALINE EARTH METALS, AND THE HEAVY METALS OF GROUPS I, II AND IV OF THE PERIODIC SYSTEM, AND (C) SAID METAL ACETATE AND SAID CARBOXYLIC ACID BEING PRESENT IN AMOUNTS SUCH THAT THE MOLE RATIO OF THE ACETIC ACID PRECURSOR OF THEMETAL ACETATE TO THE CARBOXYLIC ACID IS FROM ABOUT 4:1 TO 40:1. 